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Touch/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A microwave beeps. Tim reaches for a bowl of hot soup in the microwave, Moby bumps into him and spills the soup on Tim's hand. TIM: Ow. Hot! Arrgh. Ow. Tim places his burned hand under a running faucet. MOBY: Beep? TIM: What? No, I didn't call you. MOBY: Beep? TIM: Oh. That was the microwave beeping. Tim reads from a typed letter. TIM: Dear Tim and Moby, how does our skin tell us when things are hot or cold? From, Kate B. Hot and cold sensations are part of your sense of touch. Touch is usually considered one of the five senses, but it's a little different from the other four. For one thing, you experience touch all over your body. Vision, hearing, smell, and taste are confined to your eyes, ears, nose, and tongue. But you can feel touch, or tactile sensations, pretty much everywhere. An image shows the five senses. The senses of vision, hearing, smell, and taste are shown with their corresponding body parts. The sense of touch is shown as affecting the entire body. MOBY: Beep? TIM: Well, touch begins at tiny nerve endings in the bottom of your skin, or dermis. An animation shows a cross section of human skin with labels for the epidermis, dermis, and nerve endings (receptors). The epidermis is the top layer of skin. The dermis is below it, as are the nerve endings. TIM: These send information about sensations to your spinal cord and then to your brain. The animation shows a finger pressing down on the skin, sending a signal through the receptors. Another animation shows a person's brain and spinal cord. The signal travels from the arm to the spinal cord and then to the brain. TIM: Not all parts of your body experience touch equally. Your hands, face, tongue, and feet have way more nerve endings than other parts of your body, so they're more sensitive to touch. Images show the body areas more sensitive to touch that Tim describes. MOBY: Beep? TIM: Well, "touch" is actually a term used to describe a whole bunch of sensations that doctors refer to as somatic senses. "Somatic" means "relating to the body." An image shows a human figure. TIM: Different sensations are handled by different types of nerve endings, or receptors. An animation shows the receptors in a cross section of human skin. TIM: The most common are for pressure and vibration, temperature, and pain. Pop-up images show symbols for these four sensations. TIM: Mechanoreceptors handle the sensations of pressure and vibration. When something touches your skin, mechanoreceptors fire, and send signals to your brain. An animation shows a finger touching the skin and the signals fired by the mechanoreceptors under the skin. TIM: Specialized mechanoreceptors called hair cells respond to vibrations, allowing you to hear sound. An animation shows hair cells inside of the ear canal responding to sound wave vibrations. TIM: Other mechanoreceptors respond to light touch, pressure, and vibration. Images show a feather brushing skin, a finger pressing downward into skin, and waves sending vibrations to the skin. TIM: There are also two types of thermoreceptors, or temperature receptors, in mammals, one for cold, and one for hot. Side by side images show ice applied to skin and a lit match placed close to skin. MOBY: Beep? TIM: Pain includes a whole bunch of sensations, from itching to tickling, to stinging. Side by side images illustrate these three sensations. TIM: Some pain nerves send their signals very slowly, unlike other touch receptors. Let's say you stub your toe. Reflexes will make you jerk your foot back quickly, but you won't actually feel the pain for another second or two, while the nerves send the signals up to your brain. An animation shows a man stubbing his toe on a rock. He jerks his foot back, a pain signal goes from his toe upwards through his body, and then he responds to the pain. This scene is shown on the stock footage "Headaches". MAN: D'oh! MOBY: Beep. TIM: Yeah, there are two other senses that are sometimes classified with the touch system: balance, and a sense called proprioception. Side by side images show a figure on a tightrope holding a balance beam, and a figure with an energy field around her. TIM: There are actually many factors that give you your sense of balance. Among them are your skin's pressure receptors which signal what parts of your body are touching the ground, and which way is down. An image shows the pressure receptors on the bottom of the feet of the man walking the tightrope. TIM: And proprioception helps you figure out where your body is in space. The image of the figure with the energy field around her is shown. MOBY: Beep? TIM: Try this: close your eyes and wave your hand in front of your face. Can you tell where your hand is? Tim does what he describes. TIM: That's proprioception at work. If those receptors were damaged, you'd have no idea where your hand was unless you were looking at it. And you couldn't walk unless you were looking directly at your feet. MOBY: Beep. Moby waves his hand in front of Tim's face. TIM: Aah, cut it out. MOBY: Beep. TIM: What do you mean, you don't have proprioceptors? MOBY: Beep. Moby waves one hand in front of Tim's face and one hand behind his head as Tim laughs. TIM: Cut it out. Category:BrainPOP Transcripts Category:BrainPOP Health Transcripts